The present invention relates to a process for producing preforms or blanks for optical fibres and to a mandrel usable for performing the process. It more particularly applies to the production of monomode or monomodel optical fibres (but obviously also to the production of multimode or multimodel optical fibres).
The known processes for producing preforms for optical fibres suffer from at least one of the following disadvantages: the optical fibres produced from the preforms are costly and/or do not have good geometrical characteristics and/or do not have a good mechanical strength.
In particular, one costly preform producing process for monomode optical fibres is known, in which a not very thick silica tube is covered on its inner face with an appropriate vitreous coating by MCVD (modified chemical vapour phase deposition) or PCVD (plasma chemical vapour phase deposition) and is then enveloped in a thick silica tube.